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Experimental physics

From Wikipedia, the free encyclopedia

Experimental physicsis the category of disciplines and sub-disciplines in the field ofphysicsthat are concerned with theobservationof physicalphenomenaandexperiments.Methods vary from discipline to discipline, from simple experiments and observations, such asGalileo's experiments,to more complicated ones, such as theLarge Hadron Collider.

Overview

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Sir Ernest Rutherford's laboratory, early 20th century. (9660575343)

Experimental physics is a branch of physics that is concerned with data acquisition, data-acquisition methods, and the detailed conceptualization (beyond simplethought experiments) and realization of laboratory experiments. It is often contrasted withtheoretical physics,which is more concerned with predicting and explaining the physical behaviour of nature than with acquiring empirical data.

Although experimental and theoretical physics are concerned with different aspects of nature, they both share the same goal of understanding it and have a symbiotic relationship. The former provides data about the universe, which can then be analyzed in order to be understood, while the latter provides explanations for the data and thus offers insight into how to better acquire data and set up experiments. Theoretical physics can also offer insight into what data is needed in order to gain a better understanding of the universe, and into what experiments to devise in order to obtain it.

The tension between experimental and theoretical aspects of physics was expressed by James Clerk Maxwell as "It is not till we attempt to bring the theoretical part of our training into contact with the practical that we begin to experience the full effect of what Faraday has called 'mental inertia' - not only the difficulty of recognizing, among the concrete objects before us, the abstract relation which we have learned from books, but the distracting pain of wrenching the mind away from the symbols to the objects, and from the objects back to the symbols. This however is the price we have to pay for new ideas." [1]

History

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As a distinct field, experimental physics was established inearly modern Europe,during what is known as theScientific Revolution,by physicists such asGalileo Galilei,Christiaan Huygens,Johannes Kepler,Blaise Pascaland SirIsaac Newton.In the early 17th century, Galileo made extensive use of experimentation to validate physical theories, which is the key idea in the modern scientific method. Galileo formulated and successfully tested several results in dynamics, in particular the law ofinertia,which later became the first law inNewton's laws of motion.In Galileo'sTwo New Sciences,a dialogue between the characters Simplicio and Salviati discuss the motion of a ship (as a moving frame) and how that ship's cargo is indifferent to its motion. Huygens used the motion of a boat along a Dutch canal to illustrate an early form of the conservation ofmomentum.

Experimental physics is considered to have reached a high point with the publication of thePhilosophiae Naturalis Principia Mathematicain 1687 by Sir Isaac Newton (1643–1727). In 1687, Newton published thePrincipia,detailing two comprehensive and successful physical laws:Newton's laws of motion,from which ariseclassical mechanics;andNewton's law of universal gravitation,which describes thefundamental forceofgravity.Both laws agreed well with experiment. ThePrincipiaalso included several theories influid dynamics.

From the late 17th century onward,thermodynamicswas developed by physicist and chemistRobert Boyle,Thomas Young,and many others. In 1733,Daniel Bernoulliused statistical arguments with classical mechanics to derive thermodynamic results, initiating the field ofstatistical mechanics.In 1798,Benjamin Thompson(Count Rumford) demonstrated the conversion of mechanical work into heat, and in 1847James Prescott Joulestated the law of conservation ofenergy,in the form of heat as well as mechanical energy.Ludwig Boltzmann,in the nineteenth century, is responsible for the modern form ofstatistical mechanics.

Besides classical mechanics and thermodynamics, another great field of experimental inquiry within physics was the nature ofelectricity.Observations in the 17th and eighteenth century by scientists such as Boyle,Stephen Gray,andBenjamin Franklincreated a foundation for later work. These observations also established our basic understanding ofelectrical chargeandcurrent.By 1808John Daltonhad discovered that atoms of different elements have different weights and proposed the moderntheory of the atom.

It wasHans Christian Ørstedwho first proposed the connection between electricity and magnetism after observing the deflection of a compass needle by a nearby electric current. By the early 1830sMichael Faradayhad demonstrated that magnetic fields and electricity could generate each other. In 1864James Clerk Maxwellpresented to theRoyal Societya set of equations that described this relationship between electricity and magnetism.Maxwell's equationsalso predicted correctly thatlightis anelectromagnetic wave.Starting with astronomy, the principles of natural philosophy crystallized into fundamentallaws of physicswhich were enunciated and improved in the succeeding centuries. By the 19th century, the sciences had segmented into multiple fields with specialized researchers and the field of physics, although logically pre-eminent, no longer could claim sole ownership of the entire field of scientific research.

Current experiments

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A view of theCMSdetector, an experimental endeavour of theLHCatCERN.

Some examples of prominent experimental physics projects are:

  • Relativistic Heavy Ion Colliderwhich collides heavy ions such asgoldions (it is the first heavy ion collider) andprotons,it is located atBrookhaven National Laboratory,on Long Island, USA.
  • HERA,which collideselectronsorpositronsand protons, and is part ofDESY,located inHamburg,Germany.
  • LHC,or the LargeHadronCollider,which completed construction in 2008 but suffered a series of setbacks. The LHC began operations in 2008, but was shut down for maintenance until the summer of 2009. It is the world's most energetic collider upon completion, it is located atCERN,on the French-Swiss border nearGeneva.The collider became fully operational March 29, 2010 a year and a half later than originally planned.[2]
  • LIGO,the Laser Interferometer Gravitational-Wave Observatory, is a large-scale physics experiment and observatory to detect cosmic gravitational waves and to develop gravitational-wave observations as an astronomical tool. Currently two LIGO observatories exist: LIGO Livingston Observatory inLivingston, Louisiana,and LIGO Hanford Observatory nearRichland,Washington.
  • JWST,or theJames WebbSpace Telescope, launched in 2021. It will be the successor to theHubble Space Telescope.It will survey the sky in the infrared region. The main goals of the JWST will be in order to understand the initial stages of the universe, galaxy formation as well as the formations of stars and planets, and the origins of life.
  • Mississippi State Axion Search(2016 completion), Light Shining Through a Wall Experiment (LSW); EM Source:.7m, 50W continuous radio wave emitter[3]

Method

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Main article:Experiment

Experimental physics uses two main methods of experimental research,controlled experiments,andnatural experiments.Controlled experiments are often used inlaboratoriesas laboratories can offer a controlled environment. Natural experiments are used, for example, inastrophysicswhen observingcelestial objectswhere control of the variables in effect is impossible.

Famous experiments

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Main article:List of experiments in physics

Famous experiments include:

Experimental techniques

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Some well-known experimental techniques include:

Prominent experimental physicists

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Famous experimental physicists include:

Timelines

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See the timelines below for listings of physics experiments.

See also

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References

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  1. ^James Clerk Maxwell, "Introductory Lecture on Experimental Physics," The Scientific Papers of James Clerk Maxwell (1890) Vol.2
  2. ^"Yes, we did it!".CERN.2010-03-29.Retrieved2010-04-16.
  3. ^The Construction of Mississippi State Axion Search

Further reading

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  • Taylor, John R. (1987).An Introduction to Error Analysis (2nd ed.).University Science Books.ISBN978-0-935702-75-0.
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